Engineering Dictionary

Ball Piston Pumps

The Ball Piston Pump is a very simple pump design. It has a rotor which revolves around an internal stator. The rotor has twelve cylinders machined out of it, and each cylinder has a ball inside which can slide in and out of the cylinder.

In the twelve cylinder model shown here, there are only thirteen moving parts in the pump -- twelve balls, and the rotor.

From TDC (Top Dead Center) the cylinders pass over the intake port for 180 degrees, then pass over the outlet port for 180 degrees.

The balls ride along a two-railed track machined into the outer housing. The balls revolve around the pump in a perfect circle.

Because the centerpoint of the circle which the balls revolve around is offset from the centerpoint of the stator and the rotor, the balls and the rotor have relative motion to each other.